Embodiments of the invention generally relate to imaging, and more particularly to a technique for reconstructing cone-beam data.
In a typical computed tomography (CT) system, an X-ray source projects a fan-shaped or cone-shaped beam, which is collimated to lie within an X-Y plane of a Cartesian coordinate system termed the “imaging plane.” The X-ray beam passes through an object being imaged, such as a medical patient, and impinges upon an array of radiation detectors. The detector array includes detector elements, each of which measures the intensity of transmitted radiation along a beam projected from the X-ray source to the particular detector element. The intensity of the transmitted radiation is dependent upon the attenuation of the X-ray beam by the object and each detector produces a separate electrical signal that is a measurement of the beam attenuation. The signals are processed and reconstructed to form images which may be evaluated themselves or which may be associated to form a volume rendering or other representation of the imaged region. In a medical context, pathologies or other structures of interest may then be located or identified from the reconstructed or rendered volume.
During the past few years, significant progress has been made in the field of cone-beam tomography. Various exact and efficient techniques that allow accurate reconstruction for many different source trajectories such as helix, saddles, variable pitch helix, circle-plus-arc, and so forth, have been developed. Progress has also been made on developing algorithms for trajectories that do not satisfy Tuy's completeness condition everywhere in the imaging volume such as for the circular trajectory and for the circular segment trajectory. These trajectories satisfy Tuy's condition only at certain points within a single plane, yet data acquired along these paths is used to reconstruct volumetric data thereby resulting in cone-beam artifacts.
Cone-beam artifacts degrade the quality of the reconstructed CT images. Moreover, as CT scanners evolve to larger coverage, this problem becomes more critical. For example, cone-beam artifacts produce shading and glaring around high contrast edges in CT images. These artifacts are undesirable and may sometimes affect the quantitative robustness of CT numbers. Moreover, currently available traditional techniques fail to provide desired imaging quality due to cone-beam artifacts. Also, use of other currently available techniques result in new artifacts being introduced due to data truncation, additional interpolation and filtering. Further, traditional techniques of cone-beam reconstruction use weighting of different parts of the data by different amounts that result in high computational cost and time.
It is therefore desirable to provide an efficient and computationally less intensive reconstruction technique and to reduce cone-beam artifacts in CT images without compromising on image quality.
Brief Description
Briefly in accordance with one aspect of the technique a method of performing a computed tomographic image reconstruction is provided. The method provides for performing a short scan of an imaging object to acquire a short scan data, performing a plurality of image reconstructions based on the short scan data wherein the plurality of image reconstructions result in a corresponding plurality of image volumes wherein the image reconstructions use different view weighting functions, filtering the plurality of image volumes such that when the volumes are added together, the frequency domain data is substantially uniformly weighted. Further, the method provides for adding the plurality of image volumes together to produce a final image volume.
In accordance with another aspect of the present technique a tomographic imaging apparatus is provided. The apparatus includes a computer programmed to perform a short scan of an imaging object to acquire short scan data; The computer is further configured to perform a plurality of image reconstructions based on the short scan data wherein the plurality of image reconstructions result in a corresponding plurality of image volumes and wherein the image reconstructions use different view weighting function. Further, the computer is programmed to filter the plurality of image volumes such that when the volumes are added together, the frequency domain data is substantially uniformly weighted, the plurality of image volumes are combined together to produce a final image volume. The tomographic imaging apparatus includes a display unit for displaying the image. Computer programs that afford functionality of the type defined by this method may also be provided by the present technique.